DALLAS, Ga.—The single runway and modest terminal building near this town about 30 miles northwest of downtown Atlanta don't look like much of a threat to the giant Hartsfield-Jackson Atlanta International Airport.

Hartsfield, with its five runways and 203 gates, is the world's busiest airport, boarding 45.8 million passengers last year.

Paulding County's five-year-old airport, which sits among forested hills off a four-lane state road, will have one gate and handle, at most, four commercial flights a day—if the government approves its plans for airline service.

But the little airport, named Silver Comet Field, is in a dogfight over that modest goal with
Delta Air Lines Inc.,
DAL 0.96%
Hartsfield's dominant carrier.

Delta is saying little publicly about its effort, except for an Atlanta Journal-Constitution opinion piece in which a senior executive said that "a second airport can quickly expand, and the impact on Hartsfield-Jackson would be significant."

The executive,
Holden Shannon,
said the airport has room for more airlines and warned that competition would threaten "Atlanta's economy."

The same executive sent a letter to the chairman of the Paulding County Commission, the airport's owner, alleging that Silver Comet's plans were hatched in secrecy, circumvented an environmental review and have put local taxpayers at risk.

In October,
Richard Anderson,
Delta's chief executive, told the Atlanta newspaper that the venture would be "an economic and community failure."

The dispute highlights the obstacles that upstarts can face in challenging major airlines or their hubs. Small airlines have long struggled to get space at airports controlled by big carriers.

New airports also have difficulty taking off, not only because of noise-averse neighbors but because most large and midsize cities are already well-served.

As the Atlanta tussle shows, however, big airlines and airports don't like rivals—even small ones.

The U.S. has 5,200 public airports, but the bulk of them serve only small private planes and corporate jets. Just 550 offer commercial flights, and new ones rarely join that list. Several decommissioned Air Force bases that tried to do so in recent years have failed to attract much airline service.

Atlanta, the nation's 9th-largest metro area, is the only city in the top 10 that lacks a secondary commercial airport. Chicago has two airports in its city limits, and New York and Los Angeles each have five within 40 miles.

Atlanta has only Hartsfield, which handles 1,000 outbound flights daily for Delta. The carrier accounts for about 78% of the airport's passenger traffic.

Late last year Propeller Investments LLC, a small New York private-equity firm that has been trying to break into the Atlanta market, signed a 40-year contract to manage the Silver Comet terminal. Officials in Paulding County (pop. 144,800) hope commercial flights and Propeller's plan to develop a small aerospace manufacturing park will create jobs.

Brett Smith,
managing director at Propeller, estimates that his firm has spent $1 million so far on Silver Comet.

Delta has "controlled and dominated the Atlanta market in a way that no other carrier has been able to in any other large metro area," he added.

Paulding County has spent roughly $3 million of its own money, about $41 million in Federal Aviation Administration grants and $7 million in state funds on the airport, which has a two-story, 23,000-square-foot terminal and a 6,000-foot runway, long enough for most single-aisle jets to land. Today the airport handles 15 to 20 private-plane flights a day, said
Blake Swafford,
its director.

The airport will get a firetruck—essential for commercial service—later this month, has a third of the required perimeter fence up and has applied to the Transportation Security Administration for screeners in its terminal, he said.

Propeller said it is in advanced talks on commercial service with
Allegiant Travel Co.
, the owner of Allegiant Air, which links small airports to Sunbelt leisure destinations, such as Las Vegas and Orlando, Fla.

Allegiant confirmed it is interested in serving Silver Comet.

Ultralow-cost carriers like Allegiant, which offer cut-rate tickets with no frills, pose a small but growing challenge to major carriers like Delta.

David Austin,
chairman of the Paulding County Commission, said the idea that infrequent commercial flights at Silver Comet would threaten Hartsfield or Delta is absurd.

"In no way, form or fashion are we going to challenge them," he said. "I am surprised they should even care about what we are doing."

Hartsfield's general manager,
Louis Miller,
doesn't believe a limited number of commercial flights at Silver Comet would have an impact on his airport.

But Mr. Miller, who is retiring, thinks Silver Comet as a second airport "isn't commercially viable or economically sound for the region," a Hartsfield spokeswoman said.

Atlanta Mayor
Kasim Reed
said recently that "the overwhelming amount of data indicate that having two airports is unhealthy." A spokeswoman for the mayor said he was referring to a 2011 study by Hartsfield and the FAA that concluded that no sites for a second major airport were feasible at that time. The study also said the issue should be revisited periodically.

Six Paulding County residents are challenging whether runway-safety and taxiway-improvement projects at Silver Comet got an adequate environmental review.

The FAA is considering their request for an administrative stay of the project approvals. The residents also are seeking judicial review of the approvals in the U.S. Court of Appeals for the District of Columbia Circuit.

The FAA said it can't comment on litigation.

Two of the residents,
Anthony Avery
and
Susan Wilkins,
also joined a state lawsuit seeking to block a planned $3.6 million county bond issue to pay for widening some of the airport's taxiways.

A county superior court ruled on Dec. 6 that the bond issue could proceed.

Mr. Avery and Ms. Wilkins said their lawyers told them not to discuss the cases.

The lead attorneys at two law firms working for county residents in the cases didn't respond to requests for comment.

A large Atlanta-based firm, the 600-lawyer Troutman Sanders LLP, has filed voluminous open-records requests with Paulding County, seeking all public records on the airport, its expansion plans and its dealings with federal, state and local governments and with Allegiant Air. The law firm, which has done past work for Delta on its lease at Hartsfield, hasn't identified its client on this issue and declined to comment.

But Mr. Austin, the county commissioner, is convinced that Delta is behind the opposition.

"It appears that Delta has orchestrated a campaign utilizing expensive attorneys to find environmental or procedural reasons to delay or stop this important project," he wrote in a recent letter to Delta's CEO.

A Delta spokesman declined to comment on the lawyers or the lawsuits.

Other county residents have begun a petition drive to halt the plan, fearing "noise pollution, cancer-causing jet fuel fallout, devastated property values, increased traffic, increased crime" and other ills, according to their website.
Cathy Helms,
an organizer of Citizens for a Better Paulding County, said Delta isn't funding the group.

Emma O'Neal
lives near the airport and opposes the expansion unless the county buys her home. She says the propeller planes haven't been too noisy. But when the airport hosted an air show recently, one F-18 fighter jet performed stunts three times over two days. "You couldn't even think," she said. "Every window in the house shook."

WSJ opens select articles to reader conversation to promote thoughtful dialogue. See the 'Join the Conversation' area to the rightbelow for stories open to conversation. For more information, please reference our community guidelines. Email feedback and questions to moderator@wsj.com.